Proceedings of the XLV Italian Society of Agricultural Genetics - SIGA Annual Congress
Salsomaggiore Terme, Italy - 26/29 September, 2001
GENETIC RELASHIONSHIPS AMONG 90 RICE CULTIVARS BY MEANS OF AFLP AND SSR MARKERS
BERRI S.*, FIORE G.**, SPADA A.***
* Dipartimento di genetica e di Biologia dei Microrganismi, Università di Milano
** Dipartimento di Biologia, Università di Milano
*** Centro di Ricerca, Ente Nazionale Risi, Castel d’Agogna (Pv)
More than 148 million hectares are cultivated to rice worldwide, equivalent to approximately 11% of total arable land. According to the FAO database, Europe contributes only 0.6% to world production, half of which produced in Italy. During the centuries plant breeding developed a wide range of rice genotypes that allowed rice diffusion and cultivation in diversified and heterogeneous environments, producing something like 120 thousands varieties. In the past decade different types of molecular markers have been proposed and used for assessing intra-specific genetic variability in rice. Here we present our results on the application of AFLP and SSR markers to estimate the genetic relationships among 90 rice cultivars, 54 of which ancient and modern Italian varieties.
AFLP Analysis. Two AFLP data sets have been produced: the EM set, derived from primer combinations for DNA double digestion with ECO RI and MSE I, and the PM set, for the pair of enzymes PST I and MSE I. The EM set is characterized by 156 polymorphic markers, with an average of 8.7 polymorphisms per primer combination. This value is lower than those found in other cereals. The Polymorphic Information Content (PIC) was also quite low (0.27). On the contrary, the PM set showed a PIC value of 0.4, which is quite high, being 0.5 the upper limit for AFLPs, but the level of polymorphism detected was lower than that of the EM set.
SSR Analysis. Twenty Simple Sequence Repeat loci, of know map position and distributed on the twelve rice chromosomes, were used for genotyping the 90 cultivars. The number of alleles per locus ranged from 3 to 13. PIC values per locus varied from 0.08 to 0.82 (being 1 the upper limit for SSRs), with an average value of 0.45. It is interesting to point out that considering the subset of 54 Italian varieties only, the average PIC value dropped to 0.36, indicating that the Italian sample is genetically very homogeneous.
The matrix of similarities among the 90 cultivars has been calculated by combining the 3 sets of data, and it allowed to produce a dendrogram and to perform the Principal Component Analysis.